body,
html {
    margin: 0;
    padding: 0;
}

/* 外面整个大盒子 */
#my-slider {
    width: 1080px;
    height: 420px;
    position: relative;
    /* 盒子居中 */
    margin: 0 auto;

}

#my-slider ul {
    width: 790px;
    height: 340px;
    /* 定位脱离文档流，四个图片叠在一起 */
    position: relative;
    /* 去除小点 */
    list-style: none;
    margin: 0;
    padding: 0;
}

/* 整体居中 */
#my-slider ul li {
    position: absolute;
}

/* 设置透明度，其他图片隐藏 */
.slider-list__item,
.slider-list__item--selected {
    opacity: 0;
}

.slider-list__item--selected {
    opacity: 1;
}

.slide-list__next::after {
    content: '>';
}

.slide-list__previous::after {
    content: '<';
}

.slide-list__next,
.slide-list__previous {
    background: rgba(0, 0, 0, 0.2);
    color: white;
    display: inline-block;
    height: 50px;
    line-height: 50px;
    font-size: 26px;
    padding: 0 10px;
    position: absolute;
    /* 标签上升50% */
    top: 50%;
    /* 因为自身高度为50 */
    margin-top: -25px;
}

/* 鼠标放经过的效果：变成小手 */
#my-slider:hover .slide-list__next,
#my-slider:hover .slide-list__previous {
    opacity: 1;
}

.slide-list__next {
    right: 0;
}

.slide-list__previous {
    left: 0;
}

/* 小圆点 */
.slide-list__control {
    background-color: rgba(255, 255, 255, 0.5);
    position: absolute;
    bottom: 0;
    left: 50%;
    /* 水平移百分之五十 */
    transform: translateX(-50%);
    padding: 3px 10px;
    border-radius: 12px;
}

.slide-list__control-buttons,
.slide-list__control-buttons--selected {
    /* 让小圆点在一行 */
    display: inline-block;
    width: 15px;
    height: 15px;
    background-color: rgba(255, 255, 255, 1);
    border-radius: 50%;
    margin: 0 3px;
    cursor: pointer;
}

.slide-list__control-buttons--selected {
    background-color: red;
}